Two-dimensional Finite Element Research Articles

Numerical study of creep in soil anchor walls - a case study

ABSTRACT One of the fundamental unknowns in geotechnical engineering, particularly in the design and analysis of retaining walls, is creep. Traditional design approaches for anchored walls often specify a certain prestressing force in the anchors while allowing minimal wall displacement. Unfortunately, the long-term effects of creep are frequently overlooked. Over time, creep leads to increasing displacement in anchored walls, changing the loads acting on stabilizing elements and diminishing the factor of safety for excavation stability. While past research has predominantly focused on short-term behaviour in anchored and nailed walls, only limited attention has been devoted to their long-term behaviour. This study addresses the existing gap by collecting data related to the long-term behaviour of anchored walls in an excavation project. Utilizing two-dimensional finite element numerical modelling, using plane-strain analyses, the study predicts the behaviour of these walls both at the end of the excavation and five years after its completion. Long-term behaviour modelling employs a history matching approach to determine creep variables. Subsequently, the study investigates horizontal wall displacements and changes in loads within the anchors over a five-year period. Through a comparison of modelling results with field measurements, the study demonstrates the model validation in forecasting horizontal displacements at various locations and changes in loads on the anchors over time. Furthermore, the proposed method for long-term deformation calculations of excavation walls enables the anticipation of when horizontal wall displacements may surpass allowable limits. This research concludes with an examination of the evolving trends in anchor loads over time, substantiated by a combination of measurements and numerical modelling.

A two-dimensional four-node quadrilateral inverse element for shape sensing and structural health monitoring

The inverse finite element method (iFEM) is a powerful tool for shape sensing and structural health monitoring and has several advantages with respect to some other existing approaches. In this study, a two-dimensional four-node quadrilateral inverse finite element formulation is presented. The element is suitable for thin structures under in-plane loading conditions. To validate the accuracy and demonstrate the capability of the inverse element, four different numerical cases are considered for different loading and boundary conditions. iFEM analysis results are compared with regular finite element analysis results as the reference solution, and very good agreement is observed between the two solutions demonstrating the capability of iFEM approach.

Solar fuels design: Porous cathodes modeling for electrochemical carbon dioxide reduction in aqueous electrolytes

The reduction of carbon dioxide emissions is crucial to reduce the atmospheric greenhouse effect, fighting climate change and global warming. Electrochemical CO2 reduction is one of the most promising carbon capture and utilization technologies, that can be powered by solar energy and used to make added-value chemicals and green fuels, providing grid-stability, energy security, and environmental benefits. A two-dimensional finite-elements model for porous electrodes was developed and validated against experimental data, allowing the design and performance improvement of a porous zinc cathode morphology and its operational conditions for an electrolyzer producing syngas via the co-electrolysis of CO2 and water. Porosity, pore length, fiber geometric shape, inlet pressure, system temperature, and catholyte flow rate were explored, and these parameters were thoroughly tuned by using the smart-search Nelder-Mead's multi-parameter optimization algorithm to achieve pronouncedly higher, industrial-relevant current density values than those previously reported, up to 263.6 mA/cm2 at an applied potential of −1.1 V vs. RHE.

Rotordynamic analyses of stiffened cylindrical structures using high-fidelity shell models

The dynamic response of various rotating stiffened cylindrical and disk structures has been performed using low- and high-fidelity two-dimensional finite element models. The methodology is based on the Carrera Unified Formulation, in which the shell models are obtained hierarchically and automatically. These theories are formulated by expanding the unknown variables over the shell thickness. Various shell models can be implemented depending on the choice of the polynomial employed in the expansion. Lagrange polynomials are considered for developing different kinematic models and for easily modeling the stiffeners. The stiffener deformation is precisely captured through higher-order models, and the mechanical continuity between the stiffeners and skin is automatically guaranteed at the Lagrange points. The linearized equations of motion include the Coriolis and initial stress contributions. Stiffened cylinders and disks with different boundary conditions are considered. The results are compared with the three-dimensional finite element solutions from the literature or obtained using commercial software.

How does mine tailings slurry solids concentration affect stability of dam embankment slope?

ABSTRACT In view of many past failures of tailings storage facilities, practising engineers have been analysing current design guidelines for different elements of these facilities, including for tailings dams. In this paper, an attempt is made to investigate how varying tailings slurry solids concentration ( c s ) affects the stability of tailings dam embankment slope. To achieve this, elaborate two-dimensional limit equilibrium and finite element simulations were conducted and a steady-state seepage analysis was performed so as to obtain accurate free surface water flux through the slope. Initially, numerical analyses were performed for the downstream embankment slope when no material is retained upstream. Subsequently, with all parameters kept constant, the same slope was then checked when water is retained upstream, and finally for varying slurry solids concentration. Special attention was paid to the boundary between sedimentation and consolidation, defined as the solids concentration limit beyond which effective stresses start to develop. From the stability analyses performed, it is found that the factor of safety of embankment slope varies nonlinearly with total unit weight of the slurry. For coal tailings slurry, factor of safety reduced from 1.24 when water is retained to 1.15 when tailings slurry with c w = 60% is retained, representing a drop by 7.3%.

The Financial Aspects behind Designing a Wind Turbine Generator

This article investigates the construction of a wind power generator requiring the lowest possible cost. The proposed model is an Axial Flux Permanent Magnet (AFPM) Synchronous Machine, which contains two iron rotors and a coreless stator between them, constructed from resin. The scientific contribution relates to the coupling of economic and technical parameters, which will clarify the feasibility, i.e., a wind turbine construction capable of producing approximately 3.5 KW, using a simple mill and a generator of nominal rotor speed 100 rpm. Such studies are few in international literature and mainly concern low levels of rotor speed in relation to the produced output power. For the generator dimensioning, analytical equations are used, while the type and the dimensions of the magnets are determined, before the start of dimensioning. The authors carried out research in the international market, ending up with specific cost-effective magnets, while trying to adjust the remaining dimensions and materials of the machine based on these cost-effective magnets and the aforementioned nominal values of the generator. The machine, whose dimensions are derived by analytical equations, was simulated and analyzed using the Two-Dimensional Finite Element Method (2D-FEM) and the Three-Dimensional Finite Element Method (3D-FEM), for comparison purposes. Moreover, an economic analysis of the generator and its individual parts was conducted. Finally, a novel idea for reducing the total generator cost is proposed, by replacing the rotor disks with rings. The investigation revealed that analytical equations can predict with satisfactory accuracy the generator’s parameters. In addition, as permanent magnets are the most expensive materials in the construction, their predetermination using low-cost magnets can reduce the construction cost. Finally, the proposed concept of a ring-shaped rotor instead of a disk rotor, provides a cost reduction of up to 20%.

Finite element investigation of cutting speed effects on the machining of Ti6Al4V alloy

In modern times, titanium alloy has a great application prospect in the medical field. Still, the pitiful machinability of titanium alloy material brings incredible difficulty to its ultra-precision cutting. This work presented the effect of parametric sensitivity analysis of the orthogonal cutting process using the finite element method, which dramatically enhances the cutting performance of Ti–6AL–4V. The simulation results are attained by applying Abaqus® explicit 6.14 software. The mechanical reaction of two-dimensional finite element models has been examined for cutting forces. Additionally, the impacts of rake angle, clearance angle, and nose radius on the stress distribution in orthogonal cutting of Ti–6AL–4V have been investigated. Also, to make certain numerical accuracy, the Johnson–Cook constitutive models for Ti6Al4V alloy are implemented. In the end, FE simulation outcomes were supported by the reported results in the literature.

Finite Element Analysis on Thermoelastic Instability of Multidisc Clutches Involving Deformation Modes of Multilayer Material Friction Disc

Abstract A two-dimensional finite element model was developed to investigate thermoelastic instability in multilayered friction discs with finite thickness, considering the deformation modes of the steel core. The model was used to simulate four unstable modes that can occur during the engagement process, and the Fourier reduction was applied to calculate the change in critical speed under these modes. Additionally, the influence of thermal physical parameters, including the elastic modulus, thermal expansion coefficient, Poisson’s ratio, and thermal conductivity of the friction pair, on thermoelastic instability was examined. The findings indicate that the critical speed of the friction pair is lower under the symmetric (friction disc)–antisymmetric (steel disc) mode compared to the other three modes. Consequently, the symmetric–antisymmetric mode is the first to be excited and serves as the dominant mode during thermoelastic instability. Moreover, there exists a specific wave number at which the system exhibits the lowest critical speed and poorest stability. Enhancing the thermal conductivity of the friction disc and steel disc, as well as reducing the thermal expansion coefficient of the steel disc and the elastic modulus and Poisson’s ratio of both discs, can improve the thermoelastic stability of the friction pair. Notably, the thermal expansion coefficient of the friction disc has minimal impact on thermoelastic instability. These results provide a theoretical foundation for exploring the relationship between the thermal failure of friction pairs and rotational speed, as well as optimizing overall performance design.

Research on Demagnetization Fault Diagnosis Method of Mine Cutting Permanent Magnet Synchronous Motor

To give timely and accurate diagnosis in the early stage of demagnetization failure for effective control and treatment, based on wavelet packet analysis, principal component analysis (PCA) dimensionality reduction, and least squares support vector machine(LSSVM), the extraction of features and the classification of demagnetization faults are completed. Since it is difficult to collect real data sets of demagnetization faults in practice, a two-dimensional finite element simulation model of permanent magnet synchronous motor (PMSM) under uniform demagnetization and partial demagnetization faults is established based on the Maxwell simulation platform. The wavelet packet analysis is used to extract the demagnetization feature of the A-phase current of the PMSM. Based on PCA dimensionality reduction, the dimensionality reduction of fault features is realized. The LSSVM is used to identify the fault and complete the fault classification. The simulation results show that the method has a high classification accuracy rate for demagnetization faults.

Simulation of Eddy Current Losses in Twisted Wires

Twisted wires made of insulated strands, known as stranded conductors or litz wires, are used in various areas where the eddy current loss within the wire needs to be reduced. These areas include induction heating, resonance-based wireless energy transfer, and certain radio frequency devices. Some litz wires consist of thousands of individual conductor strands that are twisted together in multiple stages, creating a hierarchical bundle structure. Computer simulations (typically using finite element analysis) are used in the optimal design of the bundle structure. However, detailed three-dimensional models are computationally demanding. In this work, a two-dimensional finite element model was presented for simulating the eddy current loss in cables made of twisted wires. The key element of the model is considering the bundle structure (generally referred to as 3D configuration conditions) within the cross-sectional model domain. The accuracy of the proposed model is tested against 3D finite element simulations. The new method is shown to be accurate, and its computational cost is by orders of magnitude lower than that of 3D models.

Analysis of low-speed blade coating flows

From industrial-scale production to small-scale fabrication of functional films, the blade coating method is used widely to apply a uniform thin liquid film on a moving substrate. However, conventional hydrodynamic models are inadequate for laboratory-scale low-speed blade coating, where capillary forces dominate. In this study, the low-speed blade coating of non-evaporative Newtonian fluids was investigated in experimental, computational and analytical approaches. The transient free boundary problem was solved utilizing a two-dimensional finite element method, and a simple viscocapillary model was developed to describe the viscous stress and capillary forces within the puddle, and predict the thickness of the wet film as a function of the speed of the substrate. Comparing the predicted film thickness with the computational results, and a flow visualization experiment of blade coating with silicone oil, respectively, confirmed the model's validity. The study indicates that the proposed model may be a useful tool for optimizing laboratory coating processes, as it provides a greater understanding of the low-speed blade coating system on a laboratory scale.

The effects of using intermittent metal part reinforcement and countersink on the strength of adhesively bonded joints

This study investigates the impact of two innovative methods, namely, intermittent metal part reinforcement and countersinking, on the strength of single lap joints (SLJs). In the former method, metal inserts are strategically integrated within the adhesive layer, while the latter involves the application of countersinks on the adherends to create conical depressions for adhesive application. The metal inserts and countersink samples were fabricated using a 5-axis CNC milling machine. Subsequently, the joints were produced by subjecting the samples to 0.15 MPa pressure and 70 °C temperature for 120 min with the aid of a hot press. Tensile tests were conducted on single lap joints (SLJs) featuring five different configurations of intermittent metal part reinforcement joints (IMRJs) with varying sizes and positions of reinforcements, as well as six countersunk reinforced joints (CRJs) with different orientations of countersinks, all while keeping the width and overlap length constant. A two-dimensional finite element (FE) model of the IMRJ was constructed using ABAQUS software, incorporating cohesive zone elements to simulate the behavior of the adhesive layer (DP 460). The model's accuracy was confirmed through experimental verification. Additionally, fractographic analysis of the failure surfaces of both types of joints was carried out. The inclusion of IMRJs and CRJs in the SLJs increased their load-carrying capacity by more than 10 % and 30 %, respectively.

A simulation of chip formation mechanism in elliptical vibration assisted cutting of nickel-based superalloy Inconel 718.

This article reveals the chip formation and the reducing of cutting force mechanisms of nickel-based superalloy Inconel 718 under elliptical vibration cutting using finite element analysis software. The results are compared with traditional cutting methods. The elliptical motion trajectory of the tool in elliptical vibration cutting machining is analyzed, and a two-dimensional finite element elliptical vibration cutting model is established. The effects of dynamic impact on the elliptical vibration cutting of Inconel 718 were discussed in terms of the surface morphology, chip formation mechanism, and cutting force reduced mechanism. The simulation results show that (1) compared with traditional cutting, the surface morphology of the workpiece machined by elliptical vibration cutting is better, and the machined surface has obvious elliptic indentation; (2) in traditional cutting, sawtooth chips are formed through shear slip, while in elliptical vibration cutting, the faster relative cutting speed , higher tool-tip temperature, and smaller material removal cross-sectional area cause a more prominent thermal softening effect in the chip formation process than that in traditional cutting, which leads to the plastic flow to be dominant in the material removal process, resulting in the strip chips; and (3) compared with traditional cutting, the normal cutting force and the tangential cutting force in elliptical vibration cutting are separately reduced about 51.4% and 60.8%.

Gradual change of vibration characteristics of steel truss structure

Abstract In order to investigate the gradual change law of vibration characteristics of steel truss structures under the influence of fatigue loading and uniform corrosion, this study combines the nonlinear cumulative fatigue damage rule, corrosion depth theory, and structural residual performance theory to establish a multi-level gradually changing performance transfer model. The relationship between structural performance and damage behavior is revealed, and a numerical analysis method for the gradual change phenomenon of vibration characteristics of steel truss structures is provided. A two-dimensional finite element analysis framework for gradual changes in vibration characteristics in steel truss structures has been developed and analyzed for a steel truss girder bridge. The results show that the correlation terms of vibration characteristics gradually decay with the increase of operation time, and the degree of decay is related to the severity of fatigue damage or corrosion damage, with the overall trend exhibiting a three-stage change.

Stability design of a geosynthetic reinforced rock cuttings wall

Rocks excavation with tunnel boring machines induces a lot of cuttings. This granular material needs to be stored. When reinforced by geosynthetics, significant tensile stresses can be obtained in the resulting composite structure which allows to build steep slopes. A real case study of a reinforced rock cuttings wall is presented in this paper. To study accurately this complex problem, two calculation methods were used: a limit equilibrium (using the Bishop criteria), classically used for these kinds of stability problems and two-dimensional finite element calculations. These two methods are different and give different results. The FE calculation is the more representative and the more conservative method for such designs when considering the studied case.

Collagen Induces Anisotropy in Fingertip Subcutaneous Tissues During Contact.

The subcutaneous mechanical response of the fingertip is highly anisotropic due to the presence of a network of collagen fibers linking the outer skin layer to the bone. The impact of this anisotropy on the fingerpad deformation, which had not been studied until now, is here demonstrated using a two-dimensional finite element model of a transverse sectionof the finger. Different distributions of fiber orientations are considered: radial (physiologic), circumferential, and random (isotropic). The three variants of the model are assessed using experimental observations of a finger pressed on a flat surface. Predictions relying on the physiological orientation of fibers best reproduce experimental trends. Our results show that the orientation of fibers significantly influences the distribution of internal strains and stresses. This leads to a sudden change in the profile of contact pressure when transitioning from sticking to slipping. Interpreted in terms of tactile perception or sensation, these variations might represent important sensory cues for partial slip detection. This is also valuable information for the development of haptic devices.

Modelling of Hybrid Steel-SMA Shear Walls with Local Strain and Reinforcement Considerations

The incorporation of Super-elastic (SE) Shape Memory Alloys (SMAs), such as Nitinol (Nickel-Titanium), presents a method of passively improving the damage resiliency of traditional reinforced concrete structural elements. This resiliency can be of particular use in seismic applications owing to the super-elastic behavior allowing for increased recentering. Currently available experimental data on hybrid slender shear walls incorporating both steel and SE-SMAs has demonstrated the recentering improvements while also highlighting that use of SE-SMAs tend to cause the formation of a predominant crack that controls the response. The ability to more accurately predict this behaviour through numerical modelling would allow for better understanding of the salient parameters affecting the response of hybrid slender shear walls. The paper herein presents a numerical modelling methodology that considered the impacts of local strain concentration as a result of a singular predominant crack formation during reverse-cyclic loading. This modelling was performed in VecTor2, a non-linear two-dimensional finite element program, in conjecture with experimental data of a hybrid steel-SMA slender shear wall and a steel-only reinforced concrete companion wall. The use of a tension stiffening constitutive model which considered local fracture was found to improve the displacement prediction capabilities of models. Additional considerations which were investigated included local reinforcement properties to reflect conditions at the wall base and accounting for the impact of strain gauge instrumentation on the location of rupture of the reinforcement. The results provide insight into the numerical modeling that captures the local strain and reinforcement conditions present in hybrid steel-SMA and reinforced concrete slender shear walls.

Enhancing efficiency of magnetic energy by implementing square-shaped materials adjacent to induction machine windings

This study provides a worthwhile method for increasing the magnetic field energy and induction machine (IM) effectiveness. The coupling between the transmitter and receiver windings in the IM system can be improved by creating materials with specific electromagnetic properties. This added material has altered the magnetic flow as well as the energy of the magnetic field. Eventually, it is possible to calculate the efficiency of the magnetic field, or the ratio of primary to secondary magnetic energy. With the use of two-dimensional finite element analysis, numerical results on five cases with various configurations of a magnetic substance have been produced. This material, which varies in length or breadth, is positioned close to the windings of the transmitter, receiver, or both. Case 3, in which the transmitter generates a magnetic field on the receiver side with a minimum energy of 0.05 J and a maximum energy of 0.015 J, is the ideal material configuration for DC current. Currently, the system efficiency is 0.29 on average. A 1 kHz transmitter's energy is constant under all conditions, but its counterpart's energy fluctuates significantly, with case 5 receiving the most energy. Therefore, case 5 turns into the optimal structural arrangement. It can be inferred that case 5 similarly dominates the other with an efficiency of 0.0026, which is much greater than that of 1 kHz efficiency, while the windings are operating at 1 MHz. This leads to stronger magnetic field coupling and increased power transfer effectiveness.

Investigation of the edge effect in composites using the ANSYS software in a two-dimensional formulation

The possibility of using the universal software ANSYS to study the concentration of interlaminar stresses near the free edges of laminated composites in a two-dimensional finite element formulation is considered. In this case, the cross-section of a rectangular four-layer composite plate of finite width with free side edges subject to uniform axial deformation is simulated. To create it, an original technique is proposed which consists in using thermal stress. The presented calculation results are in good agreement with the results of other authors.

Performance of 2D-spectral finite element method in dynamic analysis of concrete gravity dams

This article presents a two-dimensional spectral finite element formulation for dynamic analysis of concrete gravity dams. Finite element method (FEM) is the one of the most extensively used analysis tools for solving problems of dynamic analysis of structures. However, it needs extensive computational resources and time for large structures, leading to the development of alternate computationally efficient modeling techniques over the past few decades. Some of these techniques are broadly termed as “Spectral Finite Element Methods” (SFEMs). Frequency domain-based SFEM (FDSFEM) and time domain-based SFEM (TDSFEM) are the most commonly used SFEMs found in the literature. This article provides a brief review of these methods identifying their key advantages and disadvantages; and explores the feasibility of applying such methods in the dynamic analysis of concrete gravity dams. Here, the TDSFEM has been used to perform the dynamic time history analysis of a concrete gravity dam due to its relative advantages over FDSFEM, which is challenging for irregular geometry and finite domain. Sensitivity analysis and convergence studies have been performed using 4-noded and 9-noded elements. The foundation of the dam has been modeled using two-dimensional infinite elements in both FEM and TDSFEM analysis, which is a novel application in the case of TDSFEM. This article quantifies the computational efficiency of TDSFEM over the conventional FEM by comparing the computation time in both methods and thus emphasizes the applicability of TDSFEM in dynamic analysis, especially in case of complex geometries and large two-dimensional structures (like concrete gravity dam). The results demonstrate the computational efficiency of TDSFEM over FEM when higher order elements are considered. Modal analysis and time history analysis results point that the use of higher order elements of TDSFEM can be a viable alternative to the use of the conventional FEM leading to significant saving in computational time with reasonable accuracy for dynamic analysis of large structures like concrete gravity dams.